This invention relates generally to laser scanning apparatus or systems and more particularly to counter mounted laser scanning apparatus or systems.
As is known laser scanners of the type used at check-out counters of retail establishments are generally of one of two types. One type is the so-called hand-held scanner. That type of scanner is a portable device arranged to be held in one's hand to aim a line of laser light at the symbol, e.g., bar code, to be read. The scanner is typically connected to an electronic cash register or computer to process the information read, e.g., record the item and price and total sale. Due to their mode of operation, e.g., the necessity to aim the device at a symbol and then actuate a button or trigger to produce the laser beam to read the symbol, hand-held scanner systems are usually limited to relatively low volume applications. For high volume scanning applications, e.g., supermarket check-out counters, where a large number of items have to be scanned quickly, stationary counter-mounted scanners are employed. Such scanners are commonly referred to as slot scanners and are mounted within a housing under the checkout counter. The housing typically includes a window at the top through which a laser beam scanning pattern is projected. The scanning pattern typically consists of plural scan lines which are either parallel to one another and/or intersect one another.
The use of a multi-line scan pattern is dictated, at least in part, by the desire to be able to read the bar code omnidirectionally, i.e., read the bar code irrespective of the orientation of the symbol with respect to the scanner. One common way of producing multi-line scanning patterns in slot scanners is by directing a laser beam onto a rotating polygonal mirror. The rotation of each mirror face has the effect of sweeping the beam directed at it through a predetermined arc, thereby creating a linear scan pattern. The swept beam is then directed to various reflecting surfaces, e.g., mirrors, which are oriented at various angles and positions with respect to one another to convert the single line pattern into the multi-line pattern and to project that pattern out of the window into the space above the window. Hence a bar code held above the window and within the pattern can be read irrespective of the orientation of the bar code.
Examples of prior art slot scanners are found in the following U.S. Pat. Nos.: 3,902,048 (Fleischer et al), 3,928,759 (Sansone), 3,988,573 (Hayosh), 3,995,166 (Hobart), 4,006,343 (Izura et al), 4,093,865 (Nickl), and 4,097,729 (Seligman et al). All of the foregoing slot scanners are of substantial size and complexity of construction. Moreover, the construction of such scanners renders them not particularly suited for automated check-out operations, e.g., operations wherein the items to be scanned are carried by some conveyor means past the scanner for reading and entry of the information into the cash register.
In my U.S. Pat. No. 4,713,532, entitled Compact Omnidirectional Laser Scanner, which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there is disclosed a counter or slot scanner which overcomes many of the size and complexity disadvantages of the prior art slot scanners. To that end the scanner of my aforenoted patent produces a rich multi-line scan pattern to effect the omnidirectional scanning of bar codes with components which are housed in a very compact and small footprint enclosure. This feature enables the scanner to be used in applications where space either below or above the counter is at a premium. Notwithstanding the advanced features of that scanner it still leaves something to be desired from the standpoint of ease of construction, assembly and suitablity for use in an automated check-out counter.
In my copending U.S. Pat. application Ser. No. 07/07/299,998, filed on Jan. 23, 1989, entitled Laser Scanner Engine with Folded Beam Path, which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there is disclosed and claimed a modular scanner ("engine") which is extremely compact in size and suitable for use in various types of scanning systems.